Observations Made on the Island of Hammerfost, for the Royal Society. By Jeremiah Dixon

XXXV. Observations made on the Island of Hammerfost, for the Royal Society. By Jeremiah Dixon. A Journal of my Observations at Hammerfost. 1769. May 7 At half past 10 A.M. anchored in Hammerfost-Bay, near the town of Hammerfost, on Hammerfost-Island. In the afternoon went on shore, to find a proper place to observe in; but found none. May 8 Went on shore again, to find a place; and, after much search and travel, fixed upon one: but, though the best this or the adjacent islands could afford, is very difficult of access. May 9 Landed the house and observatory. May 10 Digging holes for fixing the clock-post, and stand for the transit-instrument. Note, the ground so much frozen and rocky, could not finish them this day. The carpenters, this day, put up the house, separate from the observatory; as there was not room left by the carpenter at Greenwich for fixing the transit-instrument. Finished the digging, and fixed up the post for the clock; also put up that part of the observatory which moves round. Note, the post for the clock was 3 feet deep in the ground. Carried the instruments on shore: the carpenters working at the observatory. Fixed up the clock, and set it a-going. Note, The upper part of the bob of the pendulum was set to scratch, marked thus \( \omega \) and the index to N° 14. It vibrated on each side of the perpendicular \( 1^\circ 30' \). Put up the quadrant. It was placed upon the stand provided for it. The stand stood on a large cask filled with water, very firmly fixed in the ground; and the box in the bottom of the stand filled with stones. Cloudy weather. Placed one thermometer without doors, and the other within the observatory; also placed the barometer in a proper place. Cloudy till 5 May 20, in the evening; when I took the following equal altitudes of the Sun. | May 20 | Sun West. | Sun East. | Point on the quadrant. | |--------|-----------|-----------|-----------------------| | | L. limb. | Up. limb. | | | | h, " | h, " | | | 9 4 42 | 9 11 5 | 21 54 18 | 22 0 44 | | | 16 26 | 59 37 | 6 5 | | | 21 44 | 22 4 54 | 11 20 | | 9 41 14| 9 47 46 | 21 17 33 | 21 24 6 | | | 46 33 | 53 8 | 22 58 | | | 52 2 | 58 33 | 28 2c | | 10 6 1 | 10 12 40+ | 20 52 24 | 20 59 10 | | | 11 28 | 18 9½ | 58 0 | | | 16 58 | 23 42 | 21 3 27 | | | | | 21 10 7 | These correspond to the above point 74, taken in the morning. From the points 72 and 74, in the above sets of observations, I find the clock on the 21st, at noon, to be 12' 53''.2 too slow, and loses at the rate of 2'' per day of sidereal time. May 22 Marked a meridian. The mark S° is distant about 2½ miles, and that N° about 2 miles. The situation would not allow me to have marks nearer. Put the clock forward, to be nearer the right ascension of the mid-heaven. This afternoon came on a most violent storm of wind, hail, and snow, which continued till Tuesday evening. Cloudy, with snow, &c. Ditto. Fixed the transit-instrument. Cloudy, snow, &c. | Date | Sun L. limb | Sun Up. limb | Sun East. | Point | |------------|-------------|--------------|-----------|-------| | 3 May 30 | 9 29 28 | 9 35 56½ | | 65,00 | | | 34 48 | 41 17 | | | | | 40 6 | 46 35 | | | | | 49 46½ | 9 56 12 | | 66,40 | | | 55 6 | 10 1 29 | | | | | 10 0 21 | 6 49 | | | | | 14 4 | 10 20 32 | | 68,40 | | | 19 22 | 25 53 | | | | | 24 43½ | 31 12 | | | | | 10 38 31 | 45 3 | | 70,40 | | | 43 53 | 50 27½ | | | | | 49 18½ | 55 52 | | | | | 2d wire. | 3d or middle wire. | 4th wire. | | | 3 May 31 | 16 34 33½ | 35 19 | | | | | 37 35+ | 36 4½ | | | Zen. dist. Sun's upper limb 86° 47' 50". | Date | Sun Up. limb | Sun East. | L. limb. | |------------|--------------|-----------|----------| | 4 June 1 | 23 46 5 | 23 52 34 | | | | 51 28 | 57 58 | | | | 56 50 | 0 3 20 | | | | 0 10 44 | 0 17 22 | | | | 16 14 | 22 54 | | | | 21 44 | 28 25 | | | | 0 31 46½ | 0 38 34 | | | | 27 23 | 44 14½ | | | | 43 3 | 49 58 | | Sun's first east limb passed the transit. Last or west limb passed at midnight. 1769 | 1769 | Sun | East | Sun | West | Point | |------|-----|------|-----|------|-------| | 24 June | Up. limb. | L. limb. | Up. limb. | L. limb. | 57° 40' | | 53 31' | 0 0 33½ | 59 20' | 0 6 27 | 12 29½ | | Very hazy. | 1st wire. | 2d wire. | 3d or middle wire. | 4th wire. | 5th wire. | | 4 39 39 | 0 40 24 | 41 10 | 41 55 | 42 40 | Sun's W. limb passed the transit. E. limb passed ditto. Zen. dist. of the Sun's upper limb 48° 5' 50''. The pendulum of the clock now vibrates 1° 20' on the left hand, and 1° 30' on the right. This afternoon the Sun being pretty well defined, adjusted the focus of the telescope to my eye, as follows.—Short eye-piece and broad little speculum I. 20th. 25th. O 19 12 to the right of O on the adjusting scale. Ditto with micrometer O O 17 I. 20th. 25th. to the right.—Long eye-piece and narrow little speculum O O 7 to left of O.—I. 20th. 25th. Long eye-piece and broad little speculum O 18 17 to the right.—These are the means of 8 or 9 trials each. The spot near the Sun's center was thus defined. | 2 June | Sun | West | Sun | East | Point | |--------|-----|------|-----|------|-------| | L. limb. | Up. limb. | L. limb. | Up. limb. | L. limb. | 70° 40' | | 10 55 1 | 11 7 2 | 22 20 26½ | 22 21 37 | 27 3½ | | 11 00 26 | 12 28 | 25 50½ | 32 26 | | 11 15 50+ | 11 22 31- | 21 53 48½ | 22 0 37 | | 21 21 | 28 3 | 59 23 | 6 9½ | | 26 55 | 33 41' | 22 4 56½ | 11 39 | Computing from this point, the Sun passed the north point of the meridian at 10h 44' 3" 4,2 per clock. | Sun | West | Sun | East | Point | |-----|------|-----|------|-------| | L. limb. | Up. limb. | L. limb. | Up. limb. | | | 11 37 3½ | 43 56½ | 21 32 1 | 21 39 3+ | 74°00 | | 42 45 | 49 42 | 37 49 | 44 45 | | | 48 26 | 55 29 | 43 33 | 50 25 | | At midnight. | 2d wire. | 3d wire. | 4th wire. | |----------|----------|-----------| | 16 41 28 | 43 13½ | 43 59½ | | 45 30½ | | Sun’s east or first limb passed the transit at midnight. Ditto west limb. Zen. dist. of the Sun’s upper limb 86° 32′ 57″. Outer arc 92° 1′ 9″ | Sun | East | Sun | West | Point | |-----|------|-----|------|-------| | Up. limb. | L. limb. | L. limb. | Up. limb. | | | 2 June 2 | 23 10 35 | 10 11 30 | 10 23 17½ | 66°40 | | 2 June 3 | 23 9 26 | 15 52½ | 16 49 | | | 14 38 | 21 9 | 22 9 | | | 23 24 20 | 30 46½ | 9 50 20 | 9 57 44 | 65°00 | | 29 37 | 36 3½ | 50 37 | 10 3 1 | | | 34 53 | 41 20 | 10 1 58½ | 8 21 | | | 23 55 8 | 9 26 47 | 9 33 15½ | | | 23 54 00 | 32 12 | 38 36 | | | 0 5 53 | 37 33 | | Computing from this point, the Sun passed the meridian at 4° 46′ 2″,52 per clock. | 0 13 18½ | 0 19 55 | 9 1 43 | 9 8 24 | 61°00 | | 18 45½ | 25 24 | 7 14½ | 13 49 | | | 24 13 | 30 55 | 12 45 | 19 20 | | Hence the clock is 11″,13 slow of sidereal time, and loses at the rate of 6″,84 per day. The mean 4° 46′ 3″. By By comparing the instant of time $16^h\ 44'\ 3''$,42 per clock the Sun passed the meridian under the Pole on the 2d of June, with the instant $16^h\ 44'\ 22''$05 per clock, it passed the meridian mark per transit instrument, I find it is $18''$,63 later per transit, that is, the mark northward stands $18''$,63 too much to the east. Now by putting up another mark at the same distance as the first, so as to correspond to the second wire, and measuring the distance between this and the first mark, I find it to be 36 feet. This increased in the ratio of the zen. dist. $86^\circ\ 48'$ to rad. gives $36,057$ feet for the space corresponding to $45'\frac{1}{2}$, the time of the Sun's passage from the second to the third or middle wire. The reason of this increase is, that all the wires in a transit instrument, except the middle one, describe lesser circles, parallel to the middle one, which describes an azimuth.—Having got what space corresponds to $45'\frac{1}{2}$, we have, by proportion, $14,76$ feet for the space, answering to $18''$,63, which the mark must be moved westward to be in the true meridian. **THE TRANSIT OF VENUS.** | Time p. clock | Saw the planet Venus upon the Sun about half immersed. | |---------------|--------------------------------------------------------| | 1769 June 3 | Not totally immersed. | | | The planet seemed to be completely upon the Sun, but no thread of light: this was an instantaneous view, and through a thin cloud. | | | The air all this time very hazy. | | | Saw Venus upon the Sun's limb, the 2d internal contact being past. After this, all cloudy as before. | **THE ECLIPSE OF THE SUN.** | Time p. clock | Micrometer | Ap. time | Value of microm. | |---------------|------------|----------|------------------| | h' '' | Inch. | | | | 2 3 23 | 3 0 20 | | | | 7 44 | 2 13 17 | | | | 10 30 | 2 9 21 | | | | 13 33 | 2 5 12 | | | | 22 5 | 4 17 21 | | | | 24 57 | 4 19 11 | | | | 30 4 | 6 14 | | | | 33 37 | 1 4 11 | | | | 21 13 48½ | 18 51,9 | | The versed sine of light | | 18 9 | 16 39,1 | | Ditto | | 20 54½ | 15 27,4 | | Ditto | | 23 57 | 14 6,14 | | Ditto | | 32 27½ | 30 22,8 | | Dist. of cusps | | 35 19 | 30 52,7 | | Ditto | | 40 25½ | 8 13,15 | | Versed sine of light | | 43 57,6 | 7 33,6 | | Ditto | Time A Table shewing the minutes and seconds answering to the divisions of the micrometer scale. | Inch. | ' | " | |-------|---|---| | 1 | 6 | 13.08 | | 2 | 12 | 26.16 | | 3 | 18 | 39.24 | | 4 | 24 | 52.32 | | 5 | 31 | 05.40 | | 2oth | ' | " | |------|---|---| | 1 | 0 | 8.654 | | 2 | 0 | 37.308 | | 3 | 0 | 55.962 | | 4 | 1 | 14.616 | | 5 | 1 | 33.270 | | 10 | 3 | 6.540 | | 15 | 4 | 39.810 | | 20 | 6 | 13.080 | | 25th | ' | " | |------|---|---| | 1 | 0 | 0.746 | | 2 | 0 | 1.492 | | 3 | 0 | 2.238 | | 4 | 1 | 2.984 | | 5 | 1 | 3.730 | | 10 | 3 | 7.460 | | 15 | 4 | 11.190 | | 20 | 6 | 14.920 | | 25 | 8 | 18.650 | ○ June 4 Took the dip of the sea from the observatory, and found it to be nearly 21'. Packing up the instruments. ♦ June 5 Got all the instruments on board the Emerald. A Table shewing the Height of the Mercury in Fahrenheit's Thermometer, within the Observatory, and without in the Shade, three Times per Day; and the Height of the Mercury in the Barometer once per Day, while at Hammerfest. | Within observatory | Without observatory | Barometer | |-------------------|--------------------|-----------| | Morn. | Noon. | Even. | Morn. | Noon. | Even. | | May 1769 | | | | | | | 15 | — | 32 | — | 32 | — | 27.3 | | 16 | 31 | 32 | 33 | 31 | 33 | 27.69 | | 17 | 34 | 36 | 32 | 31 | 35 | 27.69 | | 18 | 34 | 36 | 37 | 34 | 37 | 27.00 | | 19 | 34 | 38 | 39 | 35 | 39 | 27.83 | | 20 | 40 | 47 | 43 | 40 | 43 | 27.80 | | 21 | 36 | 36 | 30 | 36 | 36 | 27.70 | | 22 | 38 | 38 | 31 | 38 | 37 | 27.00 | | 23 | 36 | 36 | 35 | 36 | 36 | 27.93 | | 24 | 36 | 36 | 36 | 36 | 36 | 27.74 | | 25 | 33 | 34 | 31 | 33 | 34 | 27.60 | | 26 | 34 | 36 | 35 | 34 | 35 | 27.50 | | 27 | 33 | 37 | 37 | 33 | 37 | 27.90 | | 28 | 32 | 35 | 34 | 33 | 36 | 27.91 | | 29 | 36 | 39 | 34 | 36 | 39 | 27.74 | | 30 | 39 | 49 | 52 | 36 | 49 | 27.65 | | 31 | 50 | 50 | 46 | 50 | 50 | 27.71 | | June | | | | | | | 1 | 43 | 43 | 40 | 43 | 43 | 27.90 | | 2 | 40 | 44 | 44 | 40 | 44 | 27.70 | | 3 | 41 | 42 | 40 | 41 | 42 | 27.60 | | 4 | 38 | 38 | 36 | 38 | 38 | 27.50 | The Latitude of the Observatory is, per obs. June 2, at noon 70° 38' 22" 4s, at noon 70° 38' 23" 4s. Note, The error of the line of collimation of the quadrant did not, upon trial, appear to be any thing worth notice. The altitudes, northward, are so low as not to be depended upon. The longitude of the observatory is (by comparing the observations of the eclipse of the Sun with those made at Greenwich), Per 1st measurement with the micrometer 1 34 40 These observations were made before the middle 2d ditto 1 34 35 of the eclipse. 3d ditto 1 34 44 13th ditto 1 35 7 These observations were after the middle. 15th ditto 1 35 13 End of the eclipse 1 35 10 1 34 55 = 23° 43' 45' East of the Royal observatory at Greenwich. Jere. Dixon. XXXVI. After-